Function returns only letters of string

user3478972 Published at Dev

30

user3478972

I wrote a program that should take a string and then return a string with only letters from the original one, but it's not working and can't figure out why. Can someone help me?

#include<stdio.h>

char *only_letters(char *s1ptr, char *s2ptr)
{
    while(*s1ptr)
    {
        if((*s1ptr >= 'a' && *s1ptr <= 'z') || (*s1ptr >= 'A' && *s1ptr <= 'Z'))
        {
            *s2ptr = *s1ptr;
            s2ptr++;
        }
        s1ptr++;
    }
    *s2ptr = '\0';
    return s2ptr;
}

int main()
{
    char *s1ptr, *s2ptr;
    printf("\n Write a string:\n");
    scanf("%s", s1ptr);
    printf("\n%s\n", *only_letters(s1ptr, s2ptr));
    return 0;
}

masoud

You have 3 problems.

s1ptr and s2ptr are two unallocated arrays which will be caused to undefined behavior.
You're incrementing s2ptr to the point which has value \0. After returning it you will have a string that just has \0.
To show a string, you must pass it without * (don't dereference it).

Try this

char *only_letters(char *s1ptr, char *s2ptr_)
{
    char *s2ptr = s2ptr_;
    while(*s1ptr)
    {
        if((*s1ptr >= 'a' && *s1ptr <= 'z') || (*s1ptr >= 'A' && *s1ptr <= 'Z'))
        {
            *s2ptr = *s1ptr;
            s2ptr++;
        }
        s1ptr++;
    }
    *s2ptr = '\0';

    return s2ptr_;
}

int main()
{
    char s1ptr[256]; // Long enough
    char s2ptr[256]; // Long enough
    printf("\n Write a string:\n");
    scanf("%s", s1ptr);
    printf("\n%s\n", only_letters(s1ptr, s2ptr));
}

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Please contact [email protected] to delete if infringement.

edited at2021-03-15

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